Cicada 2A
Standard Engine 100
LT: 2x ER PPC, 3SHS
RT: 2x ER PPC, 3SHS
As long as people ignore you, you can poke them from far away. It shuts down on every alpha. Forget about chain firing, ER PPC cycle faster than the heat dissipates. Oh, did I mention there's barely armor on this thing?

On caustic, I only managed 5 or 6 alphas before the game ends, though. Usually, either I die or we win/loose before I can fire more.
Haven't tried DHS yet, there's enough room, but it's probably not worth it.